Gilenya becomes the first MS medication that can be taken daily in pill form, and it joins a small clutch of injectable medications that sometimes go unused because they can be difficult to administer and have bothersome or painful side effects, including flulike symptoms and pain at the site of injection.

At the same time, physicians who conduct MS research and care for patients with the neurodegenerative disorder cautioned that potential safety issues that arose in clinical trials will require continued monitoring.

, which makes Gilenya, had already abandoned its effort to seek FDA approval of a higher dose of the drug, after several clinical trials found it raised the rate of serious side effects without offering patients greater improvement in their symptoms.

The newly approved drug works differently than other MS therapies currently in use. It reduces the circulation and the penetration into the brain of immune cells that cause inflammatory damage to brain cells and the fatty sheaths that protect the connections between them. In relapsing-remitting multiple sclerosis, which accounts for the majority of cases worldwide, episodes of inflammation in the brain leave lesions that can result in progressively disabling problems with mobility and cognition.

showed that compared with subjects taking a dummy pill, patients who took fingolimod had roughly half the number of MS relapses annually. A second trial compared relapse rates in subjects taking fingolimod with those of subjects taking the injectable

that patients and physicians have sought. But reducing relapses brings measurable benefits for MS patients, because each episode typically results in cumulatively greater disability.

Because it is a "highly welcomed alternative to injections," Gilenya is predicted to become a leading treatment for MS in a market expected to reach $2.4 billion in 2019, according to Trung Huynh, an analyst with the market research firm